Balloon catheter

ABSTRACT

A balloon catheter having a distal ballon, and a catheter extending from the proximal end of the balloon, out of the body, forming a conduit for ballon inflation fluid, is sized and adapted, with the balloon deflated to a relatively small size, for introduction of the balloon into the body, and the balloon is adapted to be inflated to a relatively larger size by introduction of inflation fluid into the balloon for outside the body via the conduit. The balloon catheter includes a vent disposed at the distal end of the balloon for selectively venting gas above a predetermined pressure from the interior of the balloon while restricting passage of inflation fluid from the balloon at operating pressure. The vent consists of a multi-winding coil extending distally from within the balloon, interstitial spaces generally between the windings of the coil being of a predetermined size selected to permit passage therethrough of gaseous molecules above a predetermined pressure, while restricting throughpassage of larger molecules of inflation fluid.

This is a divisional of application Ser. No. 890,819, filed July 28,1986, now U.S. Pat. No. 4,715,378.

BACKGROUND OF THE INVENTION

The invention relates to balloon catheters adapted for introduction intopassageways and organs of the body. The catheter is typically introducedwith the balloon in deflated condition for ease of insertion and tominimize the size of the opening required. Once in the desired position,the balloon is inflated by introducing fluid, i.e., liquid or gas,through the lumen of the catheter into the balloon.

In certain procedures, particularly where escape of inflating fluidwithin the body, e.g., due to perforation of the balloon, couldadversely affect a patient's health, the fluid is carefully selected. Anexample is coronary angioplasty, a procedure for enlarging the flowdiameter of arteries of the heart involving repeated inflation anddeflation of a low profile dilatation balloon. Saline or contrast mediais used as the inflating fluid because introduction of gas into thecoronary arteries could be fatal. During filling of the balloon andcatheter prior to commencing the procedure, all gas must be vented fromthe device. Samson (1986, U.S. Pat. No. 4,582,181, not conceded to beprior art to this application) uses a hypodermic tube inserted from theproximal end of the catheter to vent the air during initial filling ofthe system with saline or contrast media.

The objectives of this invention include providing a balloon constructedto selectively vent gas during filling with inflation fluid; providingsuch a balloon that may be vented without need for accessory items;providing such a balloon which can vented and prepared for insertion inmuch reduced time as compared to prior art devices; providing a ballooncatheter of such construction, having a balloon of low profile andcatheter of relatively small diameter; and providing such a ballooncatheter suitable for coronary angioplasty.

SUMMARY OF THE INVENTION

According to the invention, a balloon catheter comprises a distalballoon, and a catheter extending from the proximal end of the balloon,out of the body, forming a conduit for balloon inflation fluid, theballoon catheter being sized and adapted, with the balloon deflated to arelatively small size, for introduction of the distal balloon into thebody, and the balloon adapted to be inflated to a relatively larger sizeby introduction of inflation fluid into the balloon from outside thebody via the conduit formed by the catheter, and the balloon catheterfurther comprises vent means disposed at the distal end of the balloonfor selectively venting gas above a predetermined pressure from theinterior of the balloon while restricting passage of inflation fluidfrom the balloon, the vent means comprising a multi-winding coilextending distally from within the balloon, interstitial spacesgenerally between the windings of the coil being of a predeterminedsmall size selected to permit passage therethrough of gaseous moleculesabove a predetermined pressure, while restricting throughpassage oflarger molecules of inflation fluid.

In preferred embodiments, the balloon catheter further comprises aguidewire extending within the catheter and terminating distally withinthe coil; the ballon catheter is in a form suitable for use in theprocedure of percutaneous transluminal coronary angioplasty; and theinterstitial spaces are of a configuration to allow the passage of airat pressure of the order of about 50 psi, and to provide sufficientrestriction to flow of inflation media to enable the balloon to retaindilation pressures of the order of about 8 to 10 atm for periods of upto the order of about 1 minute.

According to another aspect of the invention, a method for forming aballoon catheter having a distal balloon, a catheter extending from theproximal end of the balloon forming a conduit for balloon inflationfluid, and a vent means disposed at the distal end of the balloon forselectively venting gas above a predetermined pressure from the interiorof the balloon while restricting passage of inflation fluid from theballoon, the vent means comprising a multi-winding coil extendingdistally from within the balloon, interstitial spaces generally betweenthe windings of the coil being of a predetermined small size selected topermit passage therethrough of gaseous molecules above a predeterminedpressure, while restricting throughpassage of larger molecules ofinflation fluid comprises the steps of placing the coil over the end ofa guidewire, positioning the balloon and catheter over the guidewire andcoil, with the guidewire extending proximally within the catheter, thecoil extending distally from within the balloon, and the distal end ofthe balloon disposed loosely about the coil, proximal of the distal endof the coil, and fixing the distal end of the balloon to the coil in amanner whereby the distal end of the balloon catheter is permeable togas molecules in said coil at pressure within the balloon above apredetermined level and are substantially impermeable to molecules ofinflation fluid at operating pressure.

In preferred embodiments of the method, the distal end of the balloon isfixed about the coil by causing the material of the balloon tip to flowwhile applying radially inwardly directed pressure to the balloon aboutthe coil, preferably the application of pressure is achieved by thesteps of: surrounding the distal end of the balloon about the coil witha sleeve of silastic material pre-soaked in freon, causing the sleeve todry to cause release of the freon and simultaneous shrinkage of thesilastic sleeve to gather the balloon tip material closely about thecoil, and applying heat to the balloon tip material to cause it to flowunder uniform hoop pressure applied by the sleeve to seal about thecoil.

Other features and advantages of the invention will be understood fromthe following description of a presently preferred embodiment, and fromthe claims.

DESCRIPTION OF THE PREFERRED EMBODIMENT Drawings

The drawings will first briefly be described.

FIG. 1 is a side view, partially in section, of a balloon catheterdevice of the invention;

FIG. 2 is an enlarged side section view of the distal portion of theballoon catheter device;

FIGS. 3, 3a and 3b are sequential side section views of the distal endof the device during formation of the vent means; and

FIGS. 4, 4a, 4b, 4c, and 4d are sequential side section views of thedistal portion of the balloon catheter device during an angioplastyprocedure.

Structure

The balloon catheter device 10 of the invention, shown in FIG. 1,consists of a catheter 12 formed of a small diameter polymer tube, e.g.,0.028 inch outside diameter and 0.019 inch inner diameter, about 140 cm.long, with balloon 14 formed close to one end. Guide wire 16, e.g.,0.010 inch diameter and 157 cm. in length, extends axially through thecatheter and tapers to a smaller diameter as it extends through balloon14 to a point of attachment 17 near the distal end 18 of the device. Theproximal end 20 of the balloon is attached to the distal end of catheter12, the catheter forming a conduit for passage of inflation fluid fromoutside the body into and out of the balloon. Guide wire 16 is connectedproximally, outside the body, to steering mechanism 21 of knownconstruction, which is used to turn the balloon distal end 18 forpassage through angular blood vessels.

Referring to FIG. 2, the distal portion of balloon catheter 10 is shownin detail. Guide wire 16 is tapered, with its outside diameterdecreasing from about 0.010 inch to 0.008 inch at position A to 0.003inch at position B; the distance from the distal tip to position B isabout 1 cm., and from position B to position A is about 2 cm. Coilspring 22 has an outside diameter of, e.g., 0.015 inch and an internaldiameter of, e.g., 0.009 inch and is fitted over the tapered end ofguide wire 16, and fixed in position on the guide wire by means ofeutectic solder 24, at the proximal end of the coil, disposed atapproximately the middle of the length of the balloon. Coil spring 22 isconstructed from spring coil wire of diameter, L₁, e.g., 0.003 inch,with at least 340 turns per inch.

Solder or a gold braze is also placed on the distal tip of the springcoil to provide a smooth introduction surface 26 of diameter, L₅, e.g.,0.015 inch. Balloon 14 is sealed to coil spring 22 near the balloondistal end, such that only air above a predetermined pressure can passfrom volume 15 within balloon 14 through the very small interstitialspaces between the windings of the coil spring 22, as shown by thearrows, to vent from the distal end of the coil. The interstitial spacesare so small as to restrict passage of liquid through these interstitialspaces, extending over region 17, along the path shown by the arrows,both between coil spring 22 and guide wire 16, and between the coilspring and balloon 14.

Balloon 14 is formed by locally expanding the tubing forming thecatheter to an outer diameter of, e.g., for use in coronary angioplasty,about 2 mm, with a wall thickness of L₂, e.g., 0.0014 inch. At distalend 28, the wall thickness, L₄, of balloon 14 is of the order of about0.005 to 0.006 inch, slightly greater than the wall thickness L₃, of thecatheter.

Manufacture

Referring to FIGS. 2, and to FIGS. 3, 3a and 3b, the process for formingthe air venting interstitial spaces in region 17 at the distal end ofthe balloon catheter will now be described.

To manufacture balloon catheter 10, the coil spring 22 and guidewire 16are inserted proximally through the balloon 14 and catheter 12 until thedistal end 19 of the balloon is disposed about the coil, with the end ofthe coil extending distally. A silastic sleeve 32 of internal diameterof about 0.010 inch (FIG. 3a) is pre-soaked in freon to cause it toexpand to an internal diameter of about 0.040 inch. The expanded sleeveis placed over the distal end 19 of balloon 14 disposed about coil 22and guidewire 16 (FIG. 3). The assembly is allowed to air dry, causingrelease of the freon, with shrinkage of the silastic sleeve to itsoriginal diameter, gathering the balloon material tightly about thecoil. The balloon tip material is then heated with a hot air gun, withthe silastic sleeve still in place, to a temperature, e.g. in the rangeof 300° to 350° F. The material of the balloon tip decreases inviscosity to flow under the uniform hoop pressure applied by thesilastic sleeve causing it to seal around the coil (FIG. 3b). (Theinflatable portion of balloon 14 is protected from the heat during thisprocess to prevent melting.) The silastic sleeve is then removed bybriefly dipping the balloon tip into freon to enlarge the sleeve, whichcan then be reused.

This process forms the interstitial spaces between the coil windings inarea 17, without sealably engaging the coil to the balloon catheter,unlike prior art devices. Adhesives are not used, nor are theynecessary.

Use

Referring to FIG. 4 et seq., the balloon catheter device 10 of theinvention is provided with balloon 14 tightly wrapped around guide wire16. Fluid 40, e.g., contrast medium, is introduced through catheter 12into balloon 14 (FIG. 4a) using a syringe or its equivalent, and theballoon catheter oriented to cause any air remaining in the balloon tobe collected at the distal end of the balloon where it is ventedaccording to the invention via the interstitial spaces between thewindings of the coil in the region indicated at 17 (shown by arrows).The interstitial spaces allow venting of air from the balloon at apressure of approximately 50 psi, but provide sufficient restriction toflow of the much higher viscosity contrast media to enable the balloonto retain dilatation pressures of 8-10 atm. for the required period(approximately 1 minute). A slight seepage of media may be visible atthe distal end of the balloon when dilatation pressures are applied, butthis will not adversely affect the patient.

The inflation fluid is withdrawn by drawing vaccuum with a syringeattached to the proximal end 41 of catheter device 10 (not shown), sothat the balloon 14 can again be tightly wrapped around guide wire 16(FIG. 4b), but now with fluid 40 within the balloon 14 and catheter 12,in place of all air. (The deflation pressure is not so great as to causeair to be drawn back into the balloon via the interstitial spaces.)

The balloon catheter is introduced percutaneously by standard procedureinto blood vessel 42 (FIG. 4c) until the balloon 14 is positioned nextto lesion 44 in vessel 42. The balloon is then inflated using fluid 40until dilatation pressures (8-10 atm.) are reached. (At this pressureweeping drops 46 of inflation fluid may appear at the distal end of thedevice, but since fluid 40 is not harmful, this weeping is acceptable.)Dilatation fluid 40 is removed from the catheter device, using asyringe, to deflate the balloon, and the catheter device is moved fortreatment at another location, or it is withdrawn from vessel 42.

Other embodiments are within the following claim.

We claim:
 1. A method of forming a ballon catheter having a distalballoon, a catheter extending from the proximal end of said balloonforming a conduit for balloon inflation fluid, and vent means disposedat the distal end of said balloon for selectively ventinq gas above apredetermined pressure from the interior of said balloon whilerestricting passage of inflation fluid from said balloon, said ventmeans comprising a multi-winding coil extending distally from withinsaid balloon, the interstitial spaces generally between the windings ofsaid coil being of a predetermined small size selected to permit passagetherethrough of gaseous molecules above a predetermined pressure whilerestricting throughpassage of larger molecules of inflation fluid,saidmethod comprising the steps of: placing said coil over the end of aguidewire, positioning the balloon and catheter over said guidewire andcoil, with said guidewire extending proximally within said catheter,said coil extending distally from within said balloon, and the distalend of said balloon disposed loosely about said coil, proximal of thedistal end of said coil, surrounding the distal end of said balloonabout said coil with a sleeve of silastic material pre-soaked in freon,applying radially inwardly directed pressure to the material of saidballoon about said coil by causing the sleeve to dry to cause release ofsaid freon and simultaneous shrinkage of the silastic sleeve to gatherthe balloon tip material closely about said coil, and applying heat tosaid baloon tip material to cause it to flow under uniform hoop pressureapplied to said sleeve to seal about said coil, thereby fixing thedistal end of said balloon to said coil in a manner whereby the distalend of said balloon catheter is permeable to gas molecules in said coilat pressure within said balloon above a predetermined level and issubstantially impermeable to molecules of inflation fluid at operatingpressure.